bio_iov_iter_unbounce(9)

💫 bio_iov_iter_unbounce(9) 💫

okay so this is a page from the Kernel API Manual — yes, that manual — and today's main character is bio_iov_iter_unbounce(9). buckle up bestie, it's a short one but it's important ✨

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🎀 NAME 🎀

bio_iov_iter_unbounce — the lil cleanup era that finishes a bounce buffer operation 🧚

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🌸 SYNOPSIS 🌸

void bio_iov_iter_unbounce (struct bio *bio , bool is_error , bool
mark_dirty );

like, that's the whole signature. three args, no cap 💅

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🦋 ARGUMENTS 🦋

• bio — the completed bio. it's done, it's served, it's giving finished-business energy 👑
• is_error — true if an I/O error occurred and the data should not be copied. so if this is true, we are not touching that data, periodt 🙈
• mark_dirty — if true, folios will be marked dirty. loud and proud about it 🔥

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💖 DESCRIPTION 💖

okay so picture this: this is a helper for direct I/O implementations that need to bounce buffer, because we need to checksum the data or perform other operations that require consistency. iykyk — sometimes you gotta take the data on a little field trip to keep everything consistent 🚌✨

it's called to complete a bio that was set up by bio_iov_iter_bounce — so, the sequel. the part two. the closing chapter 🎬

what does it actually do? it copies data back for reads, and marks the original folios dirty if requested, and then frees the bounce buffer. so basically: copy back, maybe mark dirty, free the buffer, exit stage left 💅

lowkey the whole vibe here is "clean up after yourself" and honestly? iconic. free the bounce buffer, bestie. don't leave it hanging 😭

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🌈 SEE ALSO 🌈

kernel file ./block/bio.c plus the whole friend group — bio_reset(9), bio_reuse(9), bio_chain(9), bio_chain_and_submit(9), bio_alloc_bioset(9), bio_kmalloc(9), bio_truncate(9), guard_bio_eod(9), bio_put(9), bio_alloc_clone(9), bio_init_clone(9), bio_full(9), __bio_add_page(9), bio_add_virt_nofail(9), bio_add_page(9), bio_add_folio(9), bio_add_vmalloc_chunk(9), bio_add_vmalloc(9), bio_iov_iter_get_pages(9), bio_iov_iter_bounce(9), bio_await(9), submit_bio_wait(9), bdev_rw_virt(9), bio_copy_data(9), bio_endio(9), bio_split(9), bio_trim(9), bioset_init(9)

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and that's the page!! mwah 💋 this one lives in ./block, dated October 2026 — so yeah, mark your calendar, screenshot it, send it to the group chat 🫶⭐